Grass Seed Calculator
Grass Seed Calculator
Work out how much grass seed to buy for a new lawn or for overseeding from the lawn’s area and the grass you are sowing, using university extension seeding rates for tall fescue, Kentucky bluegrass, ryegrass, fine fescue, bermudagrass, zoysia and more. The page gives pounds and kilograms of seed, the number of bags, and what a bag will cover.
Seed for your lawn, grass by grass
What one bag covers
New lawn rates are pounds of pure seed per 1,000 sq ft: tall fescue 6 to 8, Kentucky bluegrass 2 to 3, perennial ryegrass 4 to 5, fine fescue 4 to 5 and sun and shade mixtures 3 to 4 from Penn State Extension; hulled bermudagrass 1 to 2, zoysiagrass 1 to 2, bahiagrass 5 and centipedegrass 0.25 to 0.5 from NC State Extension. Overseeding into a living lawn uses a 25 to 50 percent lower rate, as NC State advises, so the page takes half the low figure to three quarters of the high one. The main figure is the middle of the range. Coated seed and blends differ, so follow the rate on the bag where it is given. The CSV, image and printed report contain the values you entered, nothing preloaded.
How to use this tool
Enter the lawn’s length and width and the area fills in, or type the area in square feet, square meters or acres. Choose the grass you are sowing and whether this is a new lawn on bare soil or overseeding a thin one, and pick the bag size you plan to buy. The pounds of seed, the range, the number of bags and the area one bag covers appear at the top.
The first chart compares every grass for the same lawn, which is useful if you are still deciding what to sow. The second shows what each bag size covers at your rate, with your lawn marked, so you can see whether one large bag or a few small ones works out better.
How the amount is worked out
Seeding rates are given in pounds of pure seed per 1,000 sq ft. The page divides your lawn area by 1,000 and multiplies by the rate: the low end, the high end, and the middle of the range, which it uses for the total. For the cool season grasses the rates are Penn State Extension’s; for the warm season grasses they are NC State Extension’s.
Overseeding sows into a lawn that still has grass, so less seed is needed to fill the gaps. NC State advises a rate 25 to 50 percent lower, so the page takes half the new lawn low figure to three quarters of its high figure. Bags are rounded up to whole bags.
Seed needed by lawn size
| Lawn | Tall fescue | Kentucky bluegrass | Perennial ryegrass | Bermudagrass | Overseed, tall fescue |
|---|---|---|---|---|---|
| 1,000 sq ft | 6 to 8 lb | 2 to 3 lb | 4 to 5 lb | 1 to 2 lb | 3 to 6 lb |
| 2,500 sq ft | 15 to 20 lb | 5 to 7.5 lb | 10 to 12.5 lb | 2.5 to 5 lb | 7.5 to 15 lb |
| 5,000 sq ft | 30 to 40 lb | 10 to 15 lb | 20 to 25 lb | 5 to 10 lb | 15 to 30 lb |
| 10,000 sq ft | 60 to 80 lb | 20 to 30 lb | 40 to 50 lb | 10 to 20 lb | 30 to 60 lb |
| 1 acre | 261 to 348 lb | 87.1 to 131 lb | 174 to 218 lb | 43.6 to 87.1 lb | 131 to 261 lb |
Pounds of pure seed, low to high end of the recommended rate. The calculator uses the middle.
A worked example you can check on paper
A new lawn measures 50 by 80 ft, which is 4,000 sq ft, or 4 thousand square feet. Tall fescue is sown at 6 to 8 lb per 1,000 sq ft, so the lawn needs 24 to 32 lb, and the middle of the range is 28 lb. Seed is often sold in 25 lb bags, so one 25 lb bag and a small 3 lb bag, or two 20 lb bags with some to spare for patching.
If the same lawn only needs thickening, the overseeding rate of 3 to 6 lb per 1,000 sq ft gives 12 to 24 lb, about 18 lb in the middle. Sown as Kentucky bluegrass instead, the new lawn would take only 8 to 12 lb, because bluegrass seed is so much smaller.
Choosing a grass
Cool season grasses grow best in spring and fall and suit the northern two thirds of the US. Tall fescue is tough and fairly drought and shade tolerant; Kentucky bluegrass spreads and repairs itself but is slow to establish; perennial ryegrass germinates fastest and is often mixed in as a nurse grass; fine fescues are the choice for dry shade.
Warm season grasses grow in summer and go brown in winter, and suit the South. Bermudagrass needs full sun and spreads fast; zoysiagrass forms a dense, slow growing turf; centipedegrass is a low maintenance grass for acid soils; bahiagrass copes with poor sandy soil. Many of these are also planted as sod or plugs rather than seed.
Getting the seed to grow
Loosen the top inch or two of soil and rake it level before sowing, or on an existing lawn mow short and rake out thatch so the seed reaches the soil. Spread half the seed in one direction and half at right angles for even cover, rake lightly so the seed is just covered, and roll or tread it in. Keep the surface moist with light, frequent watering until the grass is up, then water less often and more deeply.
Mistakes that catch people out
Sowing far above the rate. Crowded seedlings stay weak. More seed does not make a thicker lawn.
Ignoring the label on coated seed. The coating adds weight, so coated seed needs more pounds for the same number of seeds. Follow the bag rate.
Using the new lawn rate to overseed. Overseeding needs 25 to 50 percent less.
Sowing at the wrong time of year. Cool season grass sown in early summer struggles through the heat; warm season grass sown in fall has no time to establish.
Letting the seedbed dry out. A germinating seed that dries out dies. The first two or three weeks of watering matter more than the amount of seed.
Popular calculations
Each opens the calculator with its own address, and every value can be changed once it is open.
Tall fescue, new lawn
Acres and square meters
Other grasses, new lawn
Overseeding
How this was checked
The engine was tested in Node against hand calculations: 1,000 sq ft of tall fescue gives exactly 7 lb in the middle of a 6 to 8 lb range; one acre gives 304.9 lb, the 43.56 thousand square feet times 7; overseeding Kentucky bluegrass gives 1 to 2.25 lb per 1,000 sq ft, half the low new lawn figure to three quarters of the high one; and 100 m² converts to 1,076.4 sq ft. The metric rate was checked the other way: 1 lb per 1,000 sq ft is 4.88 g per square meter.
Every address in the lists above was then opened and checked for a distinct title, the right answer, charts that render, and clean CSV, image and print output containing only that calculation, at desktop, tablet and phone widths.
Common questions
How much grass seed do I need for 1,000 square feet?
It depends on the grass. For a new lawn, tall fescue takes 6 to 8 lb per 1,000 sq ft, perennial ryegrass and fine fescue 4 to 5 lb, Kentucky bluegrass 2 to 3 lb, and bermudagrass or zoysiagrass 1 to 2 lb. Overseeding a thin lawn takes 25 to 50 percent less.
How much grass seed do I need for an acre?
An acre is 43,560 sq ft, or 43.56 thousand square feet. At 6 to 8 lb per 1,000 sq ft that is 261 to 348 lb of tall fescue, about 305 lb in the middle of the range. Kentucky bluegrass at 2 to 3 lb takes 87 to 131 lb.
How much seed should I use to overseed?
NC State Extension advises a seeding rate 25 to 50 percent lower than for a new lawn when sowing into existing grass. For tall fescue that is about 3 to 6 lb per 1,000 sq ft, and for Kentucky bluegrass about 1 to 2.25 lb.
Can you put down too much grass seed?
Yes. Seedlings that are too crowded compete for light, water and nutrients, stay weak and are more prone to disease. Sowing at the recommended rate with good seed to soil contact gives a denser lawn than doubling the seed.
Why does tall fescue need so much more seed than bluegrass?
Tall fescue seed is much bigger. A pound holds a couple of hundred thousand seeds, while a pound of Kentucky bluegrass holds well over a million, so fewer pounds of bluegrass put down more seeds per square foot.
When is the best time to sow grass seed?
Cool season grasses such as tall fescue, bluegrass and ryegrass do best sown in late summer or early fall, when the soil is warm and the weeds are slowing down. Warm season grasses such as bermudagrass, zoysia and centipede are sown in late spring or early summer once the soil has warmed.
Related Calculators and Reference
- Square Footage Calculator: for lawns that are not simple rectangles.
- Mulch and Soil Calculator: topsoil to level the seedbed, in cubic yards and bags.
- Area Converter: acres, hectares and square meters.
- Grams to Ounces Converter: for small amounts of seed weighed in the kitchen.
- Gravel Calculator: for paths and edging around the new lawn.
- Sod Calculator: square feet, slabs and pallets of sod for a new lawn.
- Fertilizer Calculator: pounds per 1,000 sq ft from the numbers on the bag.
- Penn State Extension: turfgrass seed and seed mixtures: the cool season seeding rates used here.